Mass Mortality and Its Environmental and Evolutionary Consequences

Hsü, Kenneth J.; He, Qing; McKenzie, Judith A.; Weissert, Helmut; Perch-Nielsen, K.; Oberhänsli, Hedy; Kelts, Kerry; LaBrecque, John L.; Tauxe, Lisa; Krähenbühl, Urs; Percival, Stephen F.; Wright, Ramil; Karpoff, Anne Marie; Petersen, N.; Tucker, Pamela D.; Poore, Richard Z.; Gombos, Andrew M.; Pisciotto, Kenneth A.; Carman, Max F.; Schreiber, Edward

doi:10.1126/science.216.4543.249

Cited by 170 publications

(42 citation statements)

References 22 publications

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“…A sudden negative δ 13 C excursion following the terminal Cretaceous mass extinction, which, perhaps uniquely, was caused by an extraterrestrial impact, was unrelated to factors discussed in the present paper, having resulted from a brief annihilation of marine phytoplankton populations that resulted in a drastic reduction of organic carbon burial (22).…”

Section: Discussionmentioning

confidence: 89%

Relation of Phanerozoic stable isotope excursions to climate, bacterial metabolism, and major extinctions

Stanley

2010

Proc. Natl. Acad. Sci. U.S.A.

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Conspicuous global stable carbon isotope excursions that are recorded in marine sedimentary rocks of Phanerozoic age and were associated with major extinctions have generally paralleled global stable oxygen isotope excursions. All of these phenomena are therefore likely to share a common origin through global climate change. Exceptional patterns for carbon isotope excursions resulted from massive carbon burial during warm intervals of widespread marine anoxic conditions. The many carbon isotope excursions that parallel those for oxygen isotopes can to a large degree be accounted for by the Q10 pattern of respiration for bacteria: As temperature changed along continental margins, where ∼90% of marine carbon burial occurs today, rates of remineralization of isotopically light carbon must have changed exponentially. This would have reduced organic carbon burial during global warming and increased it during global cooling. Also contributing to the δ 13 C excursions have been release and uptake of methane by clathrates, the positive correlation between temperature and degree of fractionation of carbon isotopes by phytoplankton at temperatures below ∼15°, and increased phytoplankton productivity during "icehouse" conditions. The Q10 pattern for bacteria and climate-related changes in clathrate volume represent positive feedbacks for climate change. paleoclimatology | paleoceanography M any possible explanations have been advanced for one or more of the abrupt excursions in the δ 13 C of marine carbonates and organic matter that have been documented in the geologic record (see Fig. 1). Most of these hypotheses have focused on factors that change the global rate of burial of organic carbon, which is isotopically light: changes in upwelling and primary productivity; fluctuations of sea level; changes in ocean dynamics, including ones affecting the extent of anoxic conditions; changes in carbonate weathering rates; release of methane from sediments; changes in nutrient input from the land to the oceans; volcanic degassing; and release of isotopically light CO 2 from the deep sea (for literature, see SI Text, Section I). Given the strong positive correlation between δ 13 C and δ 18 O excursions in shallow marine sediments (Fig. 1), however, parsimony suggests that one or more unifying explanations should be sought to explain all of these phenomena.Missing from previous explanations for geologically brief δ 13 C excursions has been a consideration of the role of microbial processes, even though microbes have an enormous global biomass and play a prominent role in the exogenic carbon cycle. Particulate organic matter in ecosystems has three possible fates: It can be consumed by primary consumers, decomposed by bacteria (or fungi, in the case of lignocellulose), or buried. The relative importance of these fates varies from place to place and time to time. For example, carbon burial on land increased markedly during the late Paleozoic, when coal swamps became widespread (1). In the oceanic realm beyond continental rises, organ...

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Section: Discussionmentioning

confidence: 89%

Relation of Phanerozoic stable isotope excursions to climate, bacterial metabolism, and major extinctions

Stanley

2010

Proc. Natl. Acad. Sci. U.S.A.

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“…Although the most dramatic effects of the terminal Cretaceous impact occurred within the first few months, resolution of such remote events on so short a time scale has proven extremely difficult; consequently, the longer term (10 3 to 10 6 yr) aftereffects that are resolvable paleontologically have received the most study (Hsu and others, 1982;Zachos and Arthur, 1986). However, a few centimeters of boundary clay were deposited in the first year 1 , which if undisturbed, can be resolved stratigraphically (Tschudy and others, 1984)-as is the case with some constituents of fallout, e.g., shocked quartz and microspherules-enabling a •Present address: Department of Earth Sciences, The Open University, Milton Keynes, MK7 6AA, United Kingdom.…”

Section: Introductionmentioning

confidence: 99%

Early environmental effects of the terminal Cretaceous impact

Gilmour

Wolbach

Anders

1990

Geological Society of America Special Papers

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Carbon and nitrogen provide a chemical and isotopic record of the immediate environmental effects of the terminal Cretaceous impact. At Woodside Creek, New Zealand, kerogen carbon is enriched 15-fold, and total sediment nitrogen 20-fold in the basal layer of the boundary clay. Both elements show marked changes in their isotopic compositions on a millimeter scale, which may reflect the rapid sweep-out of plankton by ejecta fallout. The enrichment of nitrogen may reflect a contribution of HNO3 acid rain from a shock-induced combination of N2 and O2, but would not be expected from volcanism.Ground truth for such sudden fallout on the oceans is obtained from the 9-cm-thick Toba ash layer in the Indian Ocean. The accumulation rates of organic carbon and carbonate rise by ~3 orders of magnitude at the base of the ash layer, but then drop by 1 to 4 orders of magnitude after 3 to 4 cm. Apparently 3 to 4 g/cm 2 of the Toba ash efficiently scavenged and buried virtually all the CaC03 and much of the particulate organic material in the ocean up to 2,000 km from the site of the eruption. Presumably the 2 to 5 g/cm 2 of Cretaceous/Tertiary (K/T) ejecta were no less efficient, in view of their much finer grain size. It is significant that the amounts of marine and land biomass at the K/T boundary are approximately equal to the steady-state global inventory (one generation), as are the amounts of other enriched terrestrial elements (As, Sb, Zn). This is expected in a catastrophic but not a gradualist scenario.:ts of the terminal Cretaceous impact, in Sharpton

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“…In continuous sections, this horizon is also marked by a distinct iridium anomaly (e.g., Alvarez et al, 1980;Hsu et al, 1982;Alvarez et al, 1984;Michel et al, 1985).…”

Section: Cretaceous/paleogene Boundarymentioning

confidence: 99%